The present invention relates to a filterability improver comprising a blend of an ethylene-vinyl acetate copolymer and naphthenic oil, useful in eliminating mineral oil base fluid effects having a significant impact on filterability performance of an oil.
Mineral oil products used in the transportation industry, for example, in engine oils, contain various amounts of dissolved long-chain paraffins (waxes), depending on their origin. At low temperatures, these paraffins precipitate as platelet-shaped crystals, sometimes with the inclusion of oil. This considerably impairs the flow properties of the mineral oil. Deposits of solids occur, which often lead to problems in the use of such mineral oil products.
In the cold season, for example, blockages occur in the filters of diesel engines which prevent reliable metering of the fuels and ultimately can even result in an interruption of the supply of fuel. The ability of mineral oil to flow is impaired in winter by the precipitation of paraffin crystals.
It is known that the undesirable crystal growth can be suppressed by suitable additives, so that the tendency of the viscosity of the oils to increase is minimized. Such additives, which are known pour-point depressants or agents which improve flow, change the size and shape of the wax crystals and, in this way, counteract increases in the viscosity of the oils.
Typical agents for improving the flow of mineral oils are copolymers of ethylene with carboxylic acid esters of vinyl alcohol. German Patent No. DE 11 47 799 B1, for example, sets forth oil-soluble copolymers of ethylene and vinyl acetate, having molecular masses between about 1,000 and about 3,000 g/mol, that are added to petroleum distillate propellants or fuels. Copolymers that contain about 60% to 99% by weight of ethylene and about 1% to 40% by weight of vinyl acetate are preferred. They are particularly effective if they have been prepared by free-radical polymerization in an inert solvent at temperatures of about 70xc2x0 C. to about 130xc2x0 C. under pressures of 35 to 2,100 atmospheres gauge, as set forth in German Patent No. DE 19 14 756 B2.
Other polymers employed as agents which improve flow contain, for example, 1-hexene, as set forth in EP 184,083 B1, or diisobutylene, as set forth in EP 203,554 B1, in addition to ethylene and vinyl acetate. Copolymers of ethylene, alkenecarboxylic acid esters, vinyl esters and/or vinyl ketones are also used as pour-point depressants and for improving the flow properties of crude oils and middle distillates as disclosed in EP 111,883 B1.
Additives that have a wide range of application, i.e. that effectively suppress precipitation of paraffins from mineral oils and mineral oil fractions of differing origin, have since become available. Nevertheless, there are cases in which they prove to be of little or even no value, either because they contribute little toward increasing the flow properties at low temperatures, they impair the filterability of mineral oil distillates above the cloud point, and/or they can be handled only unsatisfactorily.
There is, therefore, a need for novel additives for improving the flow properties of petroleums or petroleum fractions in which the additives of the prior art have little or even no effect. There is also a need of novel additives that provide adequate filterability of petroleum distillates above the cloud point, and that are usable without problems.
The invention relates to an additive comprising a blend of an alkyl ester copolymer, preferably an ethylene-vinyl acetate copolymer, and naphthenic oil. The invention further relates to the use of such alkyl ester copolymers for improving the flow properties of mineral oils. The invention further relates to the use of the additive comprising a blend of an alkyl ester polymer in a fluid filter system. In particular, the novel additive is used to improve filterability of heavy base oils containing wax materials. Further, the novel additive is used to promote extended drain of gear oil lubricants in connection with 5 xcexcm filtration systems.
According to the present invention, the additive can be employed for improving flow both in crude oils and in the products of further processing obtained from the crude oil by distillation. However, its use in mineral oil distillates is preferred. Most preferably, the additive according to the present invention is employed in manual transmission oils, axle factory fill oils, and extended drain oils when used in conjunction with driveline oil filtration. Such an example is used in a fill-for-life gearbox system utilizing a 5 xcexcm filtration system in the sump. The filter is used to extend the life of the gearbox by removing any foreign matter of significant size from the lubricant and by minimizing the potential for abrasive corrosion that has a catalytic effect on wear leading to gear failure. The additive of the present invention prevents filter blockage of such a filter due to wax formation.